Jennifer Hyman and Jenny Fleiss, Rent the Runway, 2010

Brian Chesky, Joe Gebbia, and Nathan Blecharczyck, Airbnb, 2010

Adam Rich and Ben Lerer, Thrillist, 2009

Lauren Bush and Ellen Gustafson, FEED Project, 2010

Jack Abraham, Milo, 2010

Tim O’Shaughnessy and Eddie Frederick, LivingSocial, 2010

Will Pearson and Mangesh Hattikudur, Mental Floss, 2007

John Goscha, Jeff Avallon, Morgan Newman, IdeaPaint, 2009

Ben Kaufman, Mophie, 2007

Garg has already moved on from her first start-up. She landed on our list last year for her innovative company Anapata, an employer-student match service, but she recently sold it for an undisclosed amount. She has now launched another Palo Alto-based company called Gobble, which matches hungry people with local chefs cooking homemade meals (think fast food meets Fresh Direct). She recently secured $1.2 million in seed funding for the new venture from investors, including Greylock Discovery Fund, Keith Rabois, and SV Angel. Read more.

Co-founders Naveen Selvadurai and Dennis Crowley are still manning the expansion of their wildly popular geo-social site and app, Foursquare. Selvaduari recently attended the Webby Awards in New York City, at which Foursquare took the award for Best Mobile Social Networking. Now boasting 8 million users (up from 2 million in 2010), the company has its sights on local advertising markets—a virtually untapped market. "I think we're in a position to do something revolutionary for local advertising," Crowley recently told Reuters. According to the company's website, Foursquare currently employs 60 people between its New York and San Francisco offices. Read more.

Rent the Runway, a haute fashion-rental website, made the 2010 list and has since hit the big time. After successfully expanding its dress rentals to include wedding apparel (for brides, bridesmaids, engagement parties, the works) in January, the company announced in May that it had received $15 million in second-round funding from Kleiner Perkins Caufield & Byers. Reuters reported the company is likely to triple its 2010 revenue (which was $20 million). The company boasts a million members, up from 750,000 last year. Read more.

In February, Airbnb, a company that connects people to unique rooms and rental spaces worldwide, hit a milestone: More than one million nights booked. The company, which has listings in 170 countries, has nearly doubled in size since landing on the 30 Under 30 list last year, and it won the South By Southwest Interactive Awards for Mobile in March. "We haven't gotten so big that we can't high five everyone in the morning," Gebbia told Inc.com recently. In May, actor-turned-businessman Ashton Kutcher invested in the company and join as a strategic adviser. But here's what has really launched the company into tech stardom: In June, it reportedly received $100 million in funding, which helps place it at a staggering $1 billion valuation. Read more.

Founded in 2005, Thrillist, a website that features activities and deals for men, recently celebrated its expansion into its 20th city. The company continues to push its presence in local markets with its new Thrillist Rewards program, which offers highly curated and local deals to members. Rich recently told the New York Times that Thrillist is on track to make $40 million this year, half of that revenue coming from the brand's new online shopping sale site JackThreads. Read more.

Though Gustafson left to start another not-for-profit called 30 Project, Bush has continued to push the FEED Project's strong social mission to end child hunger through sales of its signature designer bags (56 million meals as of last year). Late last summer, FEED partnered with Lord & Taylor to sell an Ikat version of the bag—all of which are made by female artisans in Guatemala. This summer, the company teamed up with a New York City bakery, The Little Cupcake Bakeshop, to sell a whole range of FEED accessories, including logo-decorated cupcakes. The company has quite a list of partnerships coming this year, with big names including Clarins, American Eagle, and Pottery Barn. Read more.

This San Francisco-based Internet company, which tracks the product information of 50,000 brick-and-mortar stores, has gone from a noteworthy start-up to full fledged internet force. In early December, mega-online retailer eBay acquired Milo for a whopping $75 million—just in time for the holiday shopping season. And this was more than just your textbook acquisition. The move was widely seen as the first major steps to merging online and offline shopping, or "commerce 3.0." Abraham is currently spearheading Local at eBay, while continuing to develop the brand’s offline reach. Read more.

The guys behind the daily discount site have been quite busy since landing on the list last year. The big news: In October, LivingSocial acquired another 30 Under 30 company, Urban Escapes, a site that organizes outdoor adventures in four major cities. In early June, the company also acquired a majority stake in French daily deal site Dealissime, while also announcing its latest expansion to the Dutch cities of Amsterdam, Rotterdam, and The Hague. With all this growth, it's hard to ignore the industry buzz that LivingSocial, which now boasts 10 million users worldwide, could soon catch up to its biggest competitor, Groupon. Read more.

Making the list back in 2007, Will Pearson and crew have continued to grow trivia brand Mental Floss at a steady rate. The company announced a new editor in chief for its magazine (circulation 100,000) and website, which boasts 13 million page views a month. The brand also continues to add to its publishing empire of more than a dozen books, including the latest trivia brain-teaser The Mental Floss History of the United States (Harper, 2010). Read more.

The trio that founded IdeaPaint, a company that makes paint that can turn surfaces into dry-erase boards, has been busy since landing on the list two years ago. Though it was launched in 2002, the company saw an explosion of growth and exposure in 2010: It launched a home line with national retailer Lowe’s Home Improvement, was featured on two episodes of ABC's Extreme Makeover: Home Edition, and Newman appeared in a British Airways ad campaign. Read more.

Kaufman founded Mophie, a company that designs and sells Apple accessories, in 2005, and landed on our list in 2007. Since then, Kaufman has sold Mophie, and launched another company: Quirky.com. The site is a virtual community of inventors, who essentially help each other make ideas into reality. As if the now 24-year-old doesn’t have enough to do, Kaufman has also recently signed on to star in a Sundance channel reality show aptly-named Quirky, which will shadow the energetic entrepreneur in his everyday life. Read more.